1. Field of the Invention
The invention relates to an ink and, more particularly, to an ink for a printer.
2. Description of Related Art
An ink jet printer, which is one type of printer, has many advantages in printing technique such as it is noiseless and high-speed while providing high-quality and color printing. According to the principle of printing by such an ink jet printer, using an ink which is a liquid at ordinary temperatures, recording on a recording paper is performed by jetting liquid ink particles directly onto the recording paper. Accordingly, print quality and print drying time are influenced by the kind of recording paper. That is, if a low-quality recording paper is used, the print quality is remarkably reduced. As to such a liquid ink, Japanese Patent Application Laid-open No. Hei 1-198671 discloses a water color ink excellent in storage, image clearness, water resistance, and light resistance, and other many patent applications have been filed. However, the print quality in using the liquid ink is not satisfactory.
In general, it is known to use a hot-melt ink as a measure for solving this defect. A hot-melt ink, having a melting point higher than room temperature, is solidified with a uniform dot diameter on a recording paper irrespective of the kind of the recording paper. Therefore, printing can be performed with a high quality on any recording paper. As such a known hot-melt ink, there has been proposed an ink containing a natural wax, U.S. Pat. No. 4,390,369; an ink containing a stearic acid, European Patent Application Publication No. 0 099 682, and an ink containing an acid or alcohol of C.sub.20 -C.sub.24 and further containing a ketone having a melting point higher than that of the acid or alcohol, U.S. Pat. No. 4,659,383. In these inks, a dye is used as a coloring matter.
Further, there has been disclosed in U.S. Pat. No. 4,659,383 and U.S. Pat. No. 4,822,418 a hot-melt ink containing a solid pigment dispersed in a wax, having a melting point higher than 65.degree. C., or a fatty acid or alcohol of C.sub.18 -C.sub.24.
However, in the conventional liquid ink and hot-melt ink for an ink jet printer, it is intended to merely consider permanence of color, age stability of ink characteristics, and print quality, and there is no consideration of ink composition regarding such functionality that the ink itself is capable of being decolored or changed in color. Thus, the printed matter to be produced by the printer is considered as a mere hard copy in the prior art.